§ 30. Legislative power. The legislative power of the city is vested in the common council thereof, and it has authority to enact ordinances, not inconsistent with law, for the government of the city and the management of its business, for the preservation of good order, peace and health, for the safety and welfare of its inhabitants and the protection and security of their property; and its authority, except as otherwise provided in this chapter, or by law, is legislative only.